Update Espressif IDF to v5.4.2

When I use mpbuild to build MicroPython for ESP32_GENERIC_C3, the build completes successfully, but after Flashing, the board resets continually with the following error: ``` E (336) i2c: CONFLICT! driver_ng is not allowed to be used with this old driver ``` This issue does not affect building for ESP32_GENERIC. Mpbuild currently uses Espressif IDF v5.4.1. This has a known fault re the I2C driver. From Google: ``` Yes, there are known issues with the I2C driver in Espressif IDF v5.4.1, particularly when using the new driver_ng and old drivers together. A conflict arises because the driver_ng is not designed to be compatible with the older I2C driver. This can lead to errors like "CONFLICT! driver_ng is not allowed to be used with this old driver", as reported in several GitHub issues. ``` Please update mpbuild to use Espressif IDF v5.4.2. A final thought. Would it be possible to allow the user to specify the toolchain as a command line parameter? This could lessen the need for you to keep mpbuild up to date. Apart from this, I am really impressed with mpbuild. Keep up the good work! PS I am building on an M1 iMac running macOS Sequoia v15.6.